/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package aggregator

import (
	"github.com/arana-db/arana/pkg/merge"
	"github.com/arana-db/arana/pkg/runtime/ast"
)

func LoadAggs(fields []ast.SelectElement) map[int]func() merge.Aggregator {
	aggMap := make(map[int]func() merge.Aggregator)
	enter := func(i int, n *ast.AggrFunction) {
		if n == nil {
			return
		}
		aggMap[i] = GetAggFromName(n.Name())
	}

	for i, field := range fields {
		if field == nil {
			continue
		}
		if f, ok := field.(*ast.SelectElementFunction); ok {
			enter(i, f.Function().(*ast.AggrFunction))
		}
	}

	return aggMap
}
